Catheter Access Port (Computed Tomography) Myelography in Intrathecal Drug Delivery Troubleshooting: A Case Series of 70 Procedures

OBJECTIVES: Intrathecal drug delivery is used for the treatment of intractable spasticity, dystonia, and pain. When the symptomatology fails to respond to therapy, the cause could be failure of the medication infusion. The purpose of this study is to assess pump catheter access port (CAP)‐myelography and CAP‐CT‐myelography as advanced imaging methods in treatment failure. MATERIALS AND METHODS: We analyzed observational routinely collected data of 70 CAP procedures with 2D/3D reconstructions and additional imaging of 53 adult patients where the cause of treatment was unclear between November 2013 and November 2018. CAP‐myelography and CAP‐CT myelography were performed with postprocessing 2D/3D reconstructions. When myelography could not be obtained or when the result did not reveal the cause of the treatment failure, additional procedures, such as noncontrast CT, MRI, lumbar puncture CT, and 111Indium‐DTPA SPECT‐CT, were performed. RESULTS: CAP fluid aspiration prior to contrast medium injection was not possible (N = 17). In one case, contrast was injected into the pump pocket unintentionally (N = 1). Of 70 procedures, 24% were unaspiratable. The remaining CAP myelography examinations (N = 52) had limited value for the diagnosis. CAP‐CT myelography (N = 50) was normal (N = 31). The abnormal results (N = 19) were dorsal dural leak (N = 5), subdural catheter position (N = 2), limited rostral flow of contrast material (N = 4), limited and abnormal contrast distribution (N = 3), obstruction of rostral flow (N = 2), a leak at the pump‐catheter connection (N = 1), and a sheared catheter localized in the pump pocket (N = 2). Limited contrast distributions were found to be false positive findings (N = 2). Four normal CT‐CAP myelographic procedures were false negatives, as the reference tests revealed a cause of intrathecal drug delivery (ITDD) failure. The CAP‐CT procedures resulted in a sensitivity of 81% (17/21) and a specificity of 93% (27/29). CONCLUSIONS: CAP‐CT myelography with 2D/3D reconstructions is an essential step in the diagnostic algorithm for cases involving ITDD failure.